Linking pollen limitation and seed dispersal effectiveness.

Seed production and dispersal are crucial ecological processes impacting plant demography, species distributions and community assembly. Plant-animal interactions commonly mediate both seed production and seed dispersal, but current research often examines pollination and seed dispersal separately, which hinders our understanding of how pollination services affect downstream dispersal services. To fill this gap, we propose a conceptual framework exploring how pollen limitation can impact the effectiveness of seed dispersal for endozoochorous and myrmecochorous plant species. We summarize the quantitative and qualitative effects of pollen limitation on plant reproduction and use Optimal Foraging Theory to predict its impact on the foraging behaviour of seed dispersers. In doing so, we offer a new framework that poses numerous hypotheses and empirical tests to investigate links between pollen limitation and seed dispersal effectiveness and, consequently, post-dispersal ecological processes occurring at different levels of biological organization. Finally, considering the importance of pollination and seed dispersal outcomes to plant eco-evolutionary dynamics, we discussed the implications of our framework for future studies exploring the demographic and evolutionary impacts of pollen limitation for animal-dispersed plants.

Noise interfere on feeding behaviour but not on food preference of saffron finches (Sicalis flaveola).

Noise pollution exerts negative well-being effects on animals, especially for captive individuals. A decrease in feeding, reproduction, attention, and an increase in stress are examples of negative effects of noise pollution on animals. Noise pollution can also negatively impact animals' lives by decreasing the efficiency of food choice: attention decrease can cause animals choose the least profitable food, which can affect their fitness. The aims of this study were to analyse the effects of noise on feeding behaviour and food preference of saffron finches. Foraging tests were performed under background sound pressure levels and under a noisy condition. The behaviours exhibited by the birds during the tests were recorded using focal sampling with instantaneous recording of behaviour every 10 s. Results showed that finches consumed more the higher energetic food, and that noise pollution did not impact food consumption by the birds. Noise changed the number of visits on the feeders, and increased the expression of the 'lower the head' and vigilance behaviours during feeding. These findings could be important for wild and captive animals because an increase in vigilance and in changes in foraging behaviour could ultimately impact their fitness. Thus, mitigation measures should be taken in relation to noise impact on wildlife, this is especially the case for captive animals, which have no chance to avoid noisy environments.

The role of habitat complexity in the survival rates of migratory (native) and sedentary (non-native) species of fish larvae

The increasing losses of original features of many riverine environments and the consequent decline of native aquatic species are now a widely recognized problem. The main river basins of South America have been undergoing constant changes in their communities of fish, with native migratory species disappearing and the rising of sedentary exotic ones. However, few studies report experiments that qualify and/or quantify this correlation. Three experiments were conducted to evaluate the predation mortality of two species of fish larvae (native and non-native) regarding their habitat features. The hypothesis that natural features of habitat (aquatic vegetation and water turbidity) controls the survival rates of fish larvae was tested. The experiments highlight the importance of community structure on population dynamics. The native fish larvae showed to be more adapted than the non-native to using the aquatic plants for refuge. The habitat complexity can be closely related to the persistence of native migratory fish species.(AU)

Foraging Oxaea flavescens bees as a function of the dynamics of abiotic factors and food resource availability from Styrax camporum flowers

We examined the abiotic factors and co-specific competition for food resources that regulate the foraging activity of Oxaea flavescens bees on Styrax camporum flowers. Foraging records were gathered during 20 min. periods at the beginning of each hour between 05:00h and 18:00h during three nonconsecutive days. Pearson correlation and linear regression tests indicated that the foraging activity of O. flavescens was associated with abiotic factors during the day. O. flavescens represented 89.9% of the observed foraging visits to S. camporum flowers. On the first day of sampling, when environmental conditions were stressful, the foraging activity of O. flavescens was significantly negatively correlated with light intensity, wind speed, and temperature, and positively correlated with relative humidity. Under those conditions, optimal foraging was little affected by the availability of floral resources. On the second and third days, however, when environmental conditions were more favorable, the principal limiting factor of O. flavescens foraging activity was nectar depletion. The maximum peak of foraging under those conditions occurred before the abiotic conditions were fully favorable, however, as the eventual depletion of floral resources resulted in unfavorable cost/benefit implications for foraging during the otherwise most adequate daylight period.(AU)

Hunters' preferences and perceptions as hunting predictors in a semiarid ecosystem.

Game meat is a resource widely exploited by rural populations in various parts of the world. In recent decades, the growth in the number of people living near conserved areas has increased the demand for game meat. In this work, based on the Social-ecological Theory of Maximization, we seek to verify the influence of cost-benefit ratio, availability, and subjective preferences (flavor) in the selection of hunted species. We interviewed game-eating people in seven communities in the Brazilian semiarid region, recording information on hunting strategies, flavor preferences, and relative abundance of game fauna. We found that people hunt for the most available species regardless of the cost-benefit of this choice. Also, flavor preference can increase the odds of a species being hunted almost 100%. Our data show that hunters may prefer species that require less capture effort, even though they have energy-efficient alternatives. We found that flavor preference is proportionally the variable with the most significant effect on the chances of a species being hunted, suggesting that traditional optimal foraging models are too simple to cover the complexity involved in the selection of game species.

Optimality Models and the Propensity Interpretation of Fitness.

The propensity account of fitness intends to solve the classical tautologicity issue by identifying fitness with a disposition, the ability to survive and reproduce. As proponents recognized early on, this account requires operational independence from actual reproductive success to avoid circularity and vacuousness charges. They suggested that operational independence is achieved by measuring fitness values through optimality models. Our goal in this article is to develop this suggestion. We show that one plausible procedure by which these independent operationalizations could be thought to take place, and which is in accordance with what is said in the optimality literature, is unsound. We provide two independent lines of reasoning to show this. We then provide a sketch of a more adequate account of the role of optimality models in evolutionary contexts and draw some consequences.

Dinámica de la dieta de Asplanchna girodi (De Guerne, 1888) en un embalse tropical, Colombia / The dynamics of the diet of Asplanchna girodi (De Guerne, 1888) inhabiting a tropical reservoir in Colombia / Dinâmica da dieta de Asplanchna girodi (De Guerne, 1888) em um reservatório tropical, Colômbia

Resumen Las interacciones bióticas como depredación, forrajeo y herbivoría han sido generalmente catalogadas como las fuerzas que determinan las variaciones espaciales y temporales de las poblaciones planctónicas, tanto de presas como de depredadores. Una especie del zooplancton, presente en aguas continentales, calificada como depredadora es el rotífero Asplanchna girodi. Sin embargo, se desconoce la composición real de su dieta, las preferencias alimentarias y la dinámica espacial y temporal en relación con sus presas o alimento. En esta investigación se determinaron las preferencias tróficas de A. girodi y su fluctuación espacio-temporal, basados en ítems verdaderamente consumidos en el medio natural, a través del análisis de los contenidos estomacales de individuos capturados en las aguas del embalse Riogrande II (Antioquia-Colombia), durante un año de muestreos realizados cada 10 días. Se observó que A. girodi presentó una preferencia trófica amplia que incluyó el forrajeo de, por lo menos, cinco taxones de algas y la depredación de ocho (8) especies de rotíferos y del cladócero Bosmina freyi. Se concluye que: 1. A. girodi es una especie omnívora, con mayor preferencia por el consumo de algas. 2. Este rotífero no fue factor de presión en la dinámica poblacional de las algas, pero posiblemente lo fue para Keratella americana. 3. No se observaron diferencias espaciales en la dieta de A. girodi, pero si existieron diferencias temporales en cuanto a la composición de la dieta, la cual estuvo determinada por la oferta de las algas, principalmente durante florecimientos de Ceratium. 4. Este tipo de dieta se enmarca dentro de los conceptos de forrajeo óptimo y oportunismo trófico, estrategias que conllevan el consumo de las especies con mayor disponibilidad (en este caso algas) y el máximo ahorro de energía, puesto que no se invierte en la búsqueda de presas específicas.

Abstract Biotic interactions such as predation, foraging and herbivory have been generally categorized as the forces that determine the spatial and temporal variations of planktonic populations, both preys and predators. A species of zooplankton, present in continental waters, classified as predator is the rotifer Asplanchna girodi. However, the true composition of its diet, dietary preferences and spatial and temporal dynamics in relation to its prey or food are unknown. In this research the trophic preferences of A. girodi and its spatio-temporal fluctuation were determined, based on items truly consumed in the natural environment, through analysis of stomach contents of individuals captured in the waters of Riogrande II reservoir (Antioquia-Colombia), during one year of sampling every 10 days. It was observed that A. girodi showed a broad trophic preference that included the foraging of, at least, five algae taxa and the predation of eight rotifer species and cladoceran Bosmina freyi. It is concluded that: 1. A. girodi is an omnivorous species, with a greater preference for the consumption of algae. 2. This rotifer was not a pressure factor in the population dynamics of the algae, but possibly it was for the Keratella americana. 3. No spatial differences were observed in the A. girodi diet, but there were temporal differences in the composition of the diet, which was determined by the algae supply, mainly during Ceratium blooms. 4. This type of diet is framed within the concepts of optimal foraging and trophic opportunism, strategies that involve the consumption of the most available species (in this case algae) and the maximum energy saving since it is not invested in the search for specific prey.

Resumo Interações bióticas como predação, forrageamento e herbivoria têm sido geralmente classificadas como as forças que determinam as variações espaciais e temporais de populações planctônicas, tanto de presas quanto de predadores. Uma espécie de zooplâncton, presente em águas continentais, classificada como predador é o rotífero Asplanchna girodi. No entanto, a composição real de sua dieta, preferências alimentares e dinâmicas espaciais e temporais em relação a suas presas ou alimentos são desconhecidas. Nesta pesquisa, as preferências tróficas de A. girodi e sua flutuação espaço-temporal foram determinadas, com base em itens verdadeiramente consumidos no ambiente natural, através da análise do conteúdo estomacal de indivíduos capturados nas águas do reservatório Riogrande II (Antioquia-Colômbia), durante um ano de amostragem a cada 10 dias. Observou-se que A. girodi apresentou uma ampla preferência trófica que incluiu o forrageamento de pelo menos cinco taxa de algas e a predação de oito (8) espécies de rotíferos e o cladocero Bosmina freyi. Conclui-se que: 1. A. girodi é uma espécie onívora, com maior preferência pelo consumo de algas. 2. Este rotífero não foi um fator de pressão na dinâmica populacional das algas, mas possivelmente foi para Keratella americana. 3. Não foram observadas diferenças espaciais na dieta de A. girodi, mas houve diferenças temporárias na composição da dieta, que foi determinado pelo fornecimento de algas, principalmente durante a floração de Ceratium. Este tipo de dieta enquadra-se nos conceitos de forrageamento ótimo e oportunismo trófico; estratégias que envolvem o consumo de espécies com maior disponibilidade (neste caso algas) e a máxima economia de energia, uma vez que não é investido na busca por presas específicas.

Harvest rates and foraging strategy of Carollia perspicillata (Chiroptera: Phyllostomidae) in an artificial food patch.

An organism's foraging strategy depends on its ability to acquire and use information from food patches. A forager that does not obtain information from a food patch should remain there for a fixed time or a fixed amount of harvest. Foragers that obtain partial or complete information from the patch should be able to estimate costs and benefits from its exploitation. The foraging strategy used by a forager can be determined using the giving-up density (GUD) technique. The GUD is the amount of food left by a forager after feeding in a patch with diminishing returns. We constructed an artificial feeder to examine the foraging strategy of the short-tailed fruit bat Carollia perspicillata (Chiroptera: Phyllostomidae). In this feeder, the bat's harvest rate declined with time, i.e., they experienced diminishing returns. When offered feeders with different initial food densities, bats consumed proportionately more from rich patches than from poor ones, but they equalized GUDs. When offered feeders with different concentrations of sugar (i.e., different energy content), the higher the sugar concentration in the food, the more they consumed. Altogether, the evidence indicates that these fruit bats used complete, unbiased information to decide how much time to stay in a food patch.

Foraging strategies of black-fronted titi monkeys (Callicebus nigrifrons) in relation to food availability in a seasonal tropical forest.

Many primates have to cope with a temporal scarcity in food availability that shapes their foraging strategies. Here we investigated the changes in diet, activity, and ranging behavior of a group of black-fronted titi monkeys (Callicebus nigrifrons) according to the availability of the main high-nutritional-density item in their diet and the foraging strategy adopted when this food is scarce. We monitored one habituated group using instantaneous scan sampling over 1 year (533 h of observation, 61 days) in a seasonal tropical forest fragment (245 ha). We simultaneously collected data on food availability with fruit traps. The titi monkeys consumed fleshy fruits, the main high-nutritional-density item of their diet, in accordance with its availability, and the availability of this item modulated the ingestion of vegetative plant parts, a relatively low-nutritional-density food. During high fleshy fruit availability, the titi monkeys consumed more fleshy fruits, flowers, and invertebrates. They also traveled more, but concentrated their activity in a central area of their home range. Conversely, during fleshy fruit scarcity, they increased the breadth of their diet, switching to one richer in seeds and vegetative plant parts, and with greater plant diversity. At the same time, they reduced most energy-demanding activities, traveling less and over shorter distances, but using their home range more broadly. Corroborating the optimal foraging theory, titi monkeys altered foraging strategies according to temporal food fluctuations and responded to low fleshy fruit availability by changing their diet, activity, and ranging behavior. The adoption of a low-cost/low-yield strategy allowed us to classify them as energy minimizers.

Costly learning: preference for familiar food persists despite negative impact on survival.

Animals often rely on events in their environment that provide information (i.e. experience) to alter their future decision-making in ways that are presumed to be beneficial. Such experience-based learning, however, does not always lead to adaptive decision-making. In this study, we use the omnivorous harvestman Heteromitobates discolor to explore the role of past diet on subsequent food choice and survival. We first tested whether a short-term homogeneous diet (rotten crickets, fresh crickets or dog food) influenced subsequent food choice (rotten cricket versus fresh cricket). We next examine the impact of diet on survival. We found that following experience with a homogeneous cricket diet, adult harvestmen displayed a learned preference for familiar food, regardless of whether it was rotten or fresh crickets; individuals experiencing dog food were equally likely to choose rotten versus fresh crickets. We additionally found that individuals that ate rotten crickets suffered shorter survival than those that ate fresh crickets. Together, our results suggest that the diet an individual experiences can lead to maladaptive food preferences-preferences that ultimately result in reduced longevity.

FORRAJEO DE Zonotrichia capensis (Passeriformes: Emberizidae) Y VALOR DEL PARCHE EN CERCAS VIVAS JÓVENES DE LA SABANA DE BOGOTÁ / Foraging Behavior of Zonotrichia capensis (Passeriformes: Emberizidae) and Patch Value in Young Live Fences in the Bogotá High Plateau

El copetón Zonotrichia capensis tiene una amplia distribución en América neotropical, es un ave tolerante a las intervenciones humanas, pero sabemos poco sobre su comportamiento de forrajeo en los Andes colombianos. Por ello, estudiamos la estrategia de forrajeo del copetón y, adicionalmente, el valor de parches alimentarios a lo largo de dos cercas vivas jóvenes (plantación < 2 años), en relación con la distancia a una zona de ronda del río Bogotá, en Cajicá, Sabana de Bogotá, Colombia. El río es un área dominada por árboles en una matriz rural a urbana. Utilizamos parches artificiales hechos de bandejas de aluminio con semillas mezcladas con arena. Determinamos la proporción de consumo entre tres parches con diferentes densidades de alimento inicial, para determinar si los copetones obtienen información del parche. Usamos también parches artificiales para determinar si la distancia al río a lo largo de dos cercas vivas jóvenes afectaba el forrajeo. Nuestros resultados indican que Z. capensis no obtuvo información del parche y no reconoció diferencias en parches con diferente densidad inicial de alimento. Adicionalmente, la distancia al río afectó el valor de los parches de forrajeo en solo una de las cercas vivas examinadas donde hubo mayor consumo cerca al río. Al parecer, la densidad inicial de alimento no afectó el nivel de explotación del parche por parte de los copetones, mientras que el valor del parche en las cercas vivas jóvenes puede estar influido por la distancia al río.

The Rufous-collared Sparrow Zonotrichia capensis is a widely distributed species in neotropical America, it is tolerant to human interventions, but we know little about its foraging ecology on the Colombian Andes. Therefore, we studied the foraging strategy and, additionally, the value of foraging patches along two young live fences (< 2 year planted) in relation to the Bogota River in Cajica, in an Andean highland plateau in Colombia. The Bogota River is one of few areas dominated by arboreal vegetation in an urban-rural matrix at the study site. We used artificial food patches made of aluminum trays with seeds mixed with sand. We measured the proportion of food consumed in patches with different initial food density to determine whether sparrows obtain information from the patch. We also used artificial patches to determine whether distance to the river affected the sparrow's foraging in two young live fences. Our results indicate that Z. capensis did not gather any information from the patch and did not differentiate patches with different amounts of food. Furthermore, the distance to the river affected the value of food patches, but only in one of the live fences, where there was higher food consumption close to the river. Apparently, the food initial-density did not affect the patch exploitation level by sparrows, but the patch value in young live fences could be influenced by distance to the river.

Branch Width and Height Influence the Incorporation of Branches into Foraging Trails and Travel Speed in Leafcutter Ants Atta cephalotes (L.) (Hymenoptera: Formicidae).

Fallen branches are often incorporated into Atta cephalotes (L.) foraging trails to optimize leaf tissue transport rates and economize trail maintenance. Recent studies in lowlands show laden A. cephalotes travel faster across fallen branches than on ground, but more slowly ascending or descending a branch. The latter is likely because (1) it is difficult to travel up or downhill and (2) bottlenecks occur when branches are narrower than preceding trail. Hence, both branch height and width should determine whether branches decrease net travel times, but no study has evaluated it yet. Laden A. cephalotes were timed in relation to branch width and height across segments preceding, accessing, across, and departing a fallen branch in the highlands of Costa Rica. Ants traveled faster on branches than on cleared segments of trunk-trail, but accelerated when ascending or descending the branch-likely because of the absence of bottlenecks during the day in the highlands. Branch size did not affect ant speed in observed branches; the majority of which (22/24) varied from 11 to 120 mm in both height and width (average 66 mm in both cases). To determine whether ants exclude branches outside this range, ants were offered the choice between branches within this range and branches that were taller/wider than 120 mm. Ants strongly preferred the former. Our results indicate that A. cephalotes can adjust their speed to compensate for the difficulty of traveling on branch slopes. More generally, branch size should be considered when studying ant foraging efficiency.

The behavioural ecology of climbing plants.

Climbing plants require an external support to grow vertically and enhance light acquisition. Vines that find a suitable support have greater performance and fitness than those that remain prostrate. Therefore, the location of a suitable support is a key process in the life history of climbing plants. Numerous studies on climbing plant behaviour have elucidated mechanistic details of support searching and attachment. Far fewer studies have addressed the ecological significance of support-finding behaviour and the factors that affect it. Without this knowledge, little progress can be made in the understanding of the evolution of support-finding behaviour in climbers. Here I review studies addressing ecological causes and consequences of support finding and use by climbing plants. I also propose the use of behavioural ecology theoretical frameworks to study climbing plant behaviour. I show how host tree attributes may determine the probability of successful colonization for the different types of climbers, and examine the evidence of environmental and genetic control of circumnutation behaviour and phenotypic responses to support availability. Cases of oriented vine growth towards supports are highlighted. I discuss functional responses of vines to the interplay between herbivory and support availability under different abiotic environments, illustrating with one study case how results comply with a theoretical framework of behavioural ecology originally conceived for animals. I conclude stressing that climbing plants are suitable study subjects for the application of behavioural-ecological theory. Further research under this framework should aim at characterizing the different stages of the support-finding process in terms of their fit with the different climbing modes and environmental settings. In particular, cost-benefit analysis of climbing plant behaviour should be helpful to infer the selective pressures that have operated to shape current climber ecological communities.

Preferential prey selection by Desmodus rotundus (E. Geoffroy, 1810, Chiroptera, Phyllostomidae) feeding on domestic herbivores in the municipality of São Pedro - SP / Seleção de presas preferenciais por Desmodus rotundus (E. Geoffroy, 1810, Chiroptera, Phyllostomidae) alimentando-se de herbívoros domésticos no município de São Pedro - SP.

In order to verify possible preferential prey selection by Desmodus rotundus feeding on domestic herbivores in the Municipality of São Pedro (São Paulo, Brazil), vampire bat attacks were surveyed at rural properties where domestic herbivores were being raised and attack frequencies of D. rotundus on the total herd and on different species were calculated. The analysis found that the most frequently attacked herbivores were cattle and horses. The chi-square test (χ2), with a significance level of 5% corroborated the comparative analysis of attack frequency in properties that had these two species. Of the two, horses were attacked more frequently, which could be a sign that D. rotundus exhibits preferential prey selection when attacking domestic herbivores. This evidence is also supported by the Optimal Foraging Theory, in which the net rate of energy consumed is higher for horses than it is for cattle. Additionally, we propose that the thinner integument of horses (relative to that of cattle) may facilitate bites by D. rotundus and thus contribute to the observed prey preference.

A fim de verificar possível seleção de presa preferencial por Desmodus rotundus alimentando-se em herbívoros domésticos no Município de São Pedro (São Paulo, Brasil), foram pesquisados ataques de morcegos hematófagos em propriedades rurais nas quais os herbívoros domésticos estavam sendo criados e foram calculadas as frequências de ataques por D. rotundus no rebanho total e nas diferentes espécies. A análise mostrou que os herbívoros mais frequentemente atacados eram os bovinos e equinos. O teste do qui-quadrado (χ2) com um nível de significância de 5% corroborou a análise comparativa da frequência de ataque em propriedades que possuíam estas duas espécies. Destas duas, os cavalos foram atacados com maior frequência, o que poderia ser um sinal de que D. rotundus apresenta seleção de presas preferenciais ao atacar herbívoros domésticos. Esta evidência também é apoiada pela Teoria do Forrageamento Ótimo, em que a taxa de energia líquida consumida é maior para cavalos do que para o gado. Além disso, propomos que o tegumento mais fino de cavalos (em relação à de bovinos) pode facilitar a mordidas por D. rotundus e, assim, contribuir para a preferência da presa observada.

Preferential prey selection by Desmodus rotundus (E. Geoffroy, 1810, Chiroptera, Phyllostomidae) feeding on domestic herbivores in the municipality of São Pedro - SP / Seleção de presas preferenciais por Desmodus rotundus (E. Geoffroy, 1810, Chiroptera, Phyllostomidae) alimentando-se de herbívoros domésticos no município de São Pedro - SP.

In order to verify possible preferential prey selection by Desmodus rotundus feeding on domestic herbivores in the Municipality of São Pedro (São Paulo, Brazil), vampire bat attacks were surveyed at rural properties where domestic herbivores were being raised and attack frequencies of D. rotundus on the total herd and on different species were calculated. The analysis found that the most frequently attacked herbivores were cattle and horses. The chi-square test (χ2), with a significance level of 5% corroborated the comparative analysis of attack frequency in properties that had these two species. Of the two, horses were attacked more frequently, which could be a sign that D. rotundus exhibits preferential prey selection when attacking domestic herbivores. This evidence is also supported by the Optimal Foraging Theory, in which the net rate of energy consumed is higher for horses than it is for cattle. Additionally, we propose that the thinner integument of horses (relative to that of cattle) may facilitate bites by D. rotundus and thus contribute to the observed prey preference.(AU)

A fim de verificar possível seleção de presa preferencial por Desmodus rotundus alimentando-se em herbívoros domésticos no Município de São Pedro (São Paulo, Brasil), foram pesquisados ataques de morcegos hematófagos em propriedades rurais nas quais os herbívoros domésticos estavam sendo criados e foram calculadas as frequências de ataques por D. rotundus no rebanho total e nas diferentes espécies. A análise mostrou que os herbívoros mais frequentemente atacados eram os bovinos e equinos. O teste do qui-quadrado (χ2) com um nível de significância de 5% corroborou a análise comparativa da frequência de ataque em propriedades que possuíam estas duas espécies. Destas duas, os cavalos foram atacados com maior frequência, o que poderia ser um sinal de que D. rotundus apresenta seleção de presas preferenciais ao atacar herbívoros domésticos. Esta evidência também é apoiada pela Teoria do Forrageamento Ótimo, em que a taxa de energia líquida consumida é maior para cavalos do que para o gado. Além disso, propomos que o tegumento mais fino de cavalos (em relação à de bovinos) pode facilitar a mordidas por D. rotundus e, assim, contribuir para a preferência da presa observada.(AU)

Gape size influences seasonal patterns of piscivore diets in three Neotropical rivers

We examined diets of four piscivores, two in the order Perciformes (Cichla temensis and C. orinocensis) and two in the order Characiformes (Boulengerella cuvieri and B. lucius), from the Cinaruco, La Guardia, and Ventuari rivers in Venezuela throughout the wet-dry seasonal cycle. The four piscivores consumed a phylogenetically and morphologically diverse group of fishes, reflecting the overall diversity of fish species in these rivers. At the start of the falling-water period, Cichla consumed large prey, especially the abundant, migratory, fish of the genus Semaprochilodus. As these relatively large prey became depleted during the dry season, Cichla tended to consume smaller prey. For Boulengerella, gape limitation precluded consumption of larger, seasonally abundant, fishes, and so prey sizes were more consistent throughout the seasonal cycle. Our findings show how prey abundance and gape limitations interact to influence seasonal patterns of predator-prey interactions.(AU)

Foram examinadas as dietas de quatro espécies de peixes piscívoros, duas da ordem Perciformes (Cichla temensis and C. orinocensis) e duas da ordem Characiformes (Boulengerella cuvieri and B. lucius), coletadas durante os ciclos de cheia e seca nos rios Cinaruco, La Guardia e Ventari, Venezuela. Os quatro piscívoros consumiram grupos de peixes filogenética e morfologicamente diversos, o que reflete a ampla diversidade de peixes nos rios estudados. No início da vazante, Cichla consumiu presas grandes, especialmente Semaprochilodus, um peixe migrador muito abundante. Com a diminuição das presas maiores durante a estação seca, Cichla tendeu a se alimentar de presas menores. Para Boulengerella, a limitação da abertura bucal impediu o consumo de peixes grandes e sazonalmente abundantes e, deste modo, o tamanho de suas presas foi menos variável ao longo do ciclo sazonal. Nossos resultados mostram como a abundância das presas e a limitação na abertura bucal interagem, influenciando os padrões de interação predador-presa.(AU)

Gape size influences seasonal patterns of piscivore diets in three Neotropical rivers

We examined diets of four piscivores, two in the order Perciformes (Cichla temensis and C. orinocensis) and two in the order Characiformes (Boulengerella cuvieri and B. lucius), from the Cinaruco, La Guardia, and Ventuari rivers in Venezuela throughout the wet-dry seasonal cycle. The four piscivores consumed a phylogenetically and morphologically diverse group of fishes, reflecting the overall diversity of fish species in these rivers. At the start of the falling-water period, Cichla consumed large prey, especially the abundant, migratory, fish of the genus Semaprochilodus. As these relatively large prey became depleted during the dry season, Cichla tended to consume smaller prey. For Boulengerella, gape limitation precluded consumption of larger, seasonally abundant, fishes, and so prey sizes were more consistent throughout the seasonal cycle. Our findings show how prey abundance and gape limitations interact to influence seasonal patterns of predator-prey interactions.

Foram examinadas as dietas de quatro espécies de peixes piscívoros, duas da ordem Perciformes (Cichla temensis and C. orinocensis) e duas da ordem Characiformes (Boulengerella cuvieri and B. lucius), coletadas durante os ciclos de cheia e seca nos rios Cinaruco, La Guardia e Ventari, Venezuela. Os quatro piscívoros consumiram grupos de peixes filogenética e morfologicamente diversos, o que reflete a ampla diversidade de peixes nos rios estudados. No início da vazante, Cichla consumiu presas grandes, especialmente Semaprochilodus, um peixe migrador muito abundante. Com a diminuição das presas maiores durante a estação seca, Cichla tendeu a se alimentar de presas menores. Para Boulengerella, a limitação da abertura bucal impediu o consumo de peixes grandes e sazonalmente abundantes e, deste modo, o tamanho de suas presas foi menos variável ao longo do ciclo sazonal. Nossos resultados mostram como a abundância das presas e a limitação na abertura bucal interagem, influenciando os padrões de interação predador-presa.